Precharged digital adder and carry circuit

ABSTRACT

Disclosed is a calculator system featuring a precharged carry propagate arithmetic logic circuit. A plurality of data registers store in parallel a plurality of multi-bit data words and are coupled in parallel to the arithmetic logic circuit for executing arithmetic and logic operations thereon. The arithmetic logic circuit is responsive to instruction words for executing either an addition or a subtraction function. A carry propagate circuit is provided for precharging a carry terminal of each bit in the ALU to a reference potential along with a circuit associated with each bit for selectively discharging the carry terminal responsive to the logic level of the previous carry signal into each bit and is further responsive to the appropriate bits of the data words. An exclusive-or adder circuit has an adder terminal precharged to a reference potential during one phase of a clock signal, and further has a discharge circuit for selectively discharging the terminal in response to logic levels of the appropriate bits of the data word and responsive to the carry signal.

United States Patent' n91 Cochran et a].

[ PRECHARGED DIGITAL ADDER AND CARRY CIRCUIT Inventors: Michael J. Cochran, Richardson;

Charles P. Grant, Jr., Dallas. both of Text.

Texas Instruments lneorporated. Dallas. Tex.

21 Filed: Sept. 13,1973 l] Appl.No.:$97.0-l8,

[73] Assignee:

Int. Cl. G06F. 7/50 Field of Search 235/l74t 175. I73. 176

References Cited UNITED STATES PATENTS 2/1973 iii/I973 iii/i973 Suzuki 235/175 Pryov 235/!75 Primary E.\'aminer-David H. Malzahn v Almruev. Agent, or Firm- -Harold Levine; Rene E. Grossmam-Thomas G. Devine EEEE url

Briley zssms PM Nov. 11, 1975 an addition-or a subtraction function. A carry propagate circuit is provided for precharging a carry terminal-of each bit in the ALU to a reference potential US. Cl. 235/174: 235Il73; 235/176 along with a'circuit associated with each bit for selectively discharging the carrvterminal responsive to the logic level of the previous carry signal into each bit and isfurther responsive to the appropriate bits of the data words. An exclusive-or adder circuit has an adder terminal precharged to a reference potential during -one phase of a clock signal. and further has a discharge circuit for selectively discharging the terminal in response to logic levels of the appropriate hits of the data word and responsive to the carry signal.

7 Claims. 41 Drawing Figures (run a) I00 I l us. Patent N0;.11,;9'75 Sheetlof63 3,919,536

U.S. Patent Nov.1l, 1975 Sheet2of63 3,919,536

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US. Patent Nov. 11, 1975 Sheet6of63 3,919,536

I I o 12 I I 12 pranch R branch v I 3 M Flag Operation I Branch of .5 M1 All Mask COr1dit1on=I M2 DPT MSB M3 DPT 1 I MA DPT c I 1 M5 LLSD 1 I 1O- (me) M6 EXP 1 M58 & M7 EXP 1 v, M8 KEYBOARD OPERATIONS I I 1 I I M9 MANT 9 g I 5 M10 WAIT OPERATIONS I M11 MLSD 5 v I I I M12 MAEX I 1 v 1 1 I M13 MLSD 1 8 Y I (ma) Ml l MMSD 1 M15 MAEX 1 I R0 A N 7 7 j R1 BIN I (Rd) R2 c N MSB R3 O+N 6 f R Shift A Relative I R5 Shift B Branch, 1 i' (RC) R6 Shift 0 Addpess R7 Shift} D 1 I I I i R8 A- I- B I I R9 C+B 3 R10 6+1), I I I I R11 A313 11' v j R R12 A+Constant 1;, R1 NBS-OP -(Ra-)' R1 C+Constant .LSB J R15 ITS-Adder (Mask LSD) V I3 I 1T =add=sh1rt le'ft I 1 b) =I=sub=shift right I1 V I- '1 I 1 r I I '1 I 2o= :-A 1 P 3 MSB Zl=0utput I/O I J. v 1 I 22=A-B o =I R ME .1. L (EFFECTIVE FOR I =I=DEO EMENT 1 (53b) 2 WHOLE INSTRUC- v Q j 'IION CYCLE WITH I I I ANY DIGIT MASK) US. Patent Nov. 11, 1975 Sheet7of 63 The following 8 bits effective only if flag operations when these l bits equal the '4 encoded state Fig 50 The following 8 bits effective only if Keyboard operations Fig. 50

I bits. I3 (NOTE: ENCODED sTATE TIMES I ARE +2 FROM ACTUAL sTATEs) (fma) LSB-J The following 1; bits (flagop's) effective only during flagmask v I excepti' E 3' 5 0 TEST FLAG A 1 TEST FLAG B 2 sET FLAG A I I2 3 sET FLAG B 2 (fd) a ZERO FLAG A A 5 ZERO FLAG B I I f 1 l 6 INVERT FLAG A c) L :7 INVERT FLAG B 10 8 :EXCH. FLAG E (fb) 9 COMPARE FLAG A B' 10 SET FLAG KR A 11 ZERO FLAG K TSB 12 COPY FLAG B-A' 13 COPY FLAG A-B lu REG 5-ELAG A S0 S3 15 REG 5-FLAG B so s3 U.S. Patent Nov.ll, 1975 Sheet9of63 3,919,536

Fig, 6a

U.S. Patent Nov.11, 197s Sheetllof63 3,919,536

TO DISPLAY ARITHMETIC CHIP Fig, 7

U.S. Patent Nov.ll, 1975 Sheet l2of63 3,919,536

Fig. 8b1 Fig. 8b2 Fig. 8b3 Fig. 8b4 Fig. 8b5

Fig. 8b6 Fig. 8b? Fig. 8b8 Fig. 8b9 Fig. BbiO Fi 8a Fig.8c1 Fig. 8c2 Fig. 8c3 Fig. 8c4

Fig. 8.;5 Fig. 8c6 g. 8c? Fig. 8c8

Fig.8d1 Fig. 8d2 Fig.8d3

Fig. 8d4 Fig. 8d5 Fig. 8d6

U.S. Patent Nov. 11,1975 Sheet 13 of 63 3,919,536

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(sax: r 1) U.S. Patent Nov.ll, 1975 Sheet l6of63 3,919,536

Fig. 8b 4 0mm cez: onzoco ANYOMO c/a we 4% SH/Ff 0 US. Patent Nov.1l, 1975 Sheet 170m 3,919,536

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U.S. Patent Nov.11,l975 Sheet l8of63 3,919,536

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f a a 7/ D L /09 EXT (slit 3) [1% How US. Patent Nov.1l, 1975 Sheet 190m 3,919,536

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1. In a calculator system having a system clock for providing a plurality of clock phases, having data memory means for storing in parallel a plurality of multi-bit data words, having arithmetic logic means divided into a plurality of stages, each stage coupled to the data memory means for receiving a selected pair of bits for executing arithmetic and logic operations in bit parallel-digit serial format and selectively connected to a precharge source, each stage comprising: a. a precharge terminal; b. means for precharging the precharge terminal to a reference potential during one phase of the system clock by selectively connecting the precharge terminal to the precharge source; c. a carry propagate circuit connected to the precharge terminal and having an output terminal, the precharge terminal being connected to receive a carry input signal, the circuit including discharge means for selectively discharging at a subsequent clock phase the precharge terminal, responsive to the logic level of the carry input signal and further responsive to the logic levels of the selected pair of bits; d. a signal terminal; e. means for precharging the signal terminal during the one phase of the clock by selectively connecting the signal terminal to the precharge source; and f. an adder circuit connected to the signal terminal and including adder discharging means for selectively discharging the signal terminal at a subsequent clock phase responsive to the logic levels of the selected pair of bits and to the logic level of the carry input signal.
 2. The calculator system according to claim 1 wherein the means for discharging the precharge terminal comprise first and second serially connected IGFETS with one main electrode of the first IGFET connected to the precharge terminal and one main electrode of the second IGFET being connected to the output terminal, the output terminal, the other main electrode of each IGFET being connected together.
 3. The calculator system according to claim 2 wherein the means for discharging the precharge terminal further comprise a third and fourth IGFET connected in series, and connected in parallel with the first and second IGFETS between the precharge terminal and the output terminal.
 4. The calculator system according to claim 3 wherein the means for discharging the precharge terminal further comprise fifth and sixth serially connected IGFETS with one main electrode of the fifth IGFET connected to the output terminal, one main electrode of the sicth IGFET connected to the precharge source and with the other main electrode of each IGFET connected together.
 5. The calculator system according to claim 4 wherein the means for discharging the adder signal terminal comprise seventh and eighth IGFETS with the seventh IGFET having one main terminal connected to the signal terminal, the eighth IGFET having one main terminal connected to the precharge source and the other main terminal of each IGFET connected together.
 6. The calculator system according to claim 5 wherein the means for discharging the adder signal terminal further comprise ninth and tenth IGFETS, connected in series, and connected in parallel with the seventh and eighth IGFETS between the signal terminal and the precharge source.
 7. The calculator system according to claim 6 and further including inverting means coupled to the means for discharging the precharge terminal and to the means for discharging the signal terminal for inverting one of the selected bits for executing a subtraction function. 